A pneumonia is an infection of the lungs. Pneumonias can be caused by a variety
of pathogens, including bacteria, viruses, and even molds or certain parasites
(less common in industrialized countries). There are many strains (types) of
bacteria that cause Pneumonia... some of them include..

1. Community-acquired pneumonias (pneumonia contracted outside the hospital).
Pneumonia in this setting can be caused by a virus (such as the
influenza virus), it can also follows a viral respiratory infection, such as
a common cold caused by a
rhinovirus. These
types of pneumonia affect millions of adults each year. Common bacterial causes
of pneumonia include
Streptococcus pneumoniae, the most common pneumonia-causing bacteria.
Other organisms, that are called "atypical bacteria" (not as common), include
species such as
Mycoplasma pneumoniae.

2. Hospital-acquired pneumonia: A pneumonia that is contracted within the
hospital is called nosocomial [no-so-co-me-all] pneumonia. Patients in hospital
are generally ill to begin with, and are thus particularly vulnerable to other
kinds of bacterial species including
Klebsiella pneumoniae and
staphylococci, which can
be very dangerous.